Trader Dan,
I have an early ASM frontier six-shooter....it also has tight chambers, compared to my rifles.
I remove the revolver cylinder & use during reloading setup to ensure loaded cartridges will chamber.
I'm using Lee 44-40 dies modified to allow me to set the shoulder back to a minimum condition.
Used this setup (3 dies) for years. I noticed some cartridges still not chambering fully in the revolver. Simple, I moved the ones not chambering into a separate carton, for rifle use only. Over time, the mouths of 44-40 cartridges will sometimes not be fully square to the reloading dies ans this seems to be part of the reason rounds ended up a bit off kilter. I found some other reasons too.
My solution was to add the Lee factory crimp die for 44-40. Seat the bullet with the original die (have the roll crimp backed all the way off), then crimp with the separate Lee die.
Solved ALL these minor, but troubling issues. I now can load the most awful looking case mouth having obvious defects....and it drops right into the ASM revolver cylinder.
I now load using a 4-station Lee Classic Turret. Works like a charm. I load so fast now that I have to pay close attention to the powder hopper.
BTW, I'm using the MAV-44 sized to .428 Deer Tallow/Beeswax lube 31 grains of FF.
Almost forgot the main trouble your having.....Crimp. If your using a roll crimp, this can affect the size of the brass (diameter) vs. the "factory Crimp" die I recomend. Totally different approach. I believe the fouling at the case mouth is preventing the roll-crimped cases to bind when the try to pass that spot in the chamber.
Next could be the amount of powder & compression. I find a load just barely up to the base of the bullet loads easiest. Drop tubes and compression aren't needed in the 44-40. It could be "ok" as long as your not bulging or needing an excessive bullet seat force & crimp (possible issues due to these conditions).
My Dad had similar issues with his Uberti 38-40 revolvers. All better now.
Slim